Induction motor



Oct. 13, 1936. A. c. DlcKsoN INDUCTION MOTOR Filed Aug 7, Y1931 I/Vx/ Patented Oct. 13, 1936 UNITED STATES PATENT OFFICE INDUCTION MOTOR Application August 7, 1931, Serial No. 555,759

8 Claims.

This invention relates to a driving device especially adapted for improving the starting characteristics of a single phase alternating current induction motor.

An object of this invention is to provide a motor of the split phase alternating current induction type which will have improved starting characteristics by the provision of a device permitting the rotation of the armature a fixed distance before it positively engages and carries the load.

Additional and incidental objects will be apparent from the following detail description taken in connection with the accompanying drawing, in which- Fig. l is avvertical section of an armature illustrating the improvements of this invention.

Fig. 2 is an end elevation.

Fig. 3 is a detail view similar to Fig. 2 partly in section.

The armature comprises a series of laminated sheets I, side coppers 2, and a core 3 mounted for rotation on a motor shaft 4. core is recessed and filled with wicking 5 saturated with lubricant to provide lubrication between the bore of the armature core 3 and the shaft 4.

The armature is positioned on the shaft 4 between a shoulder 6 and a sleeve 1 with suiiicient clearance to allow freedom of rotation of the armature with respect to the shaft.

A collar 8, having a radially projecting arm 9, is securely fastened to the motor shaft 4 by means of set screws I and a shaft key II. A counterbored hole I2 is machined in the arm 9 perpendicularly to the radius of the collar 8. A pin I3 is positioned in the hole I2 having a shoulder seated against the bottom of the counterbore. A spring I4 has one end pressing against the inner end of the pin I3 and its other end seated against a plug I5 threaded into the hole I2.

A stud I6 is threaded longitudinally into the laminations I of the armature and is positioned so that when the armature is rotated the stud I6 will strike the outer end of the pin I3. When the stud I6 contacts with the pin I3 the spring I4 is compressed thereby acting as a bumper to prevent rigid impact of the parts. The resiliently supported pin I3, and the stud I6 also serves to provide a yielding connection between the armature and the motor shaft during operation of the motor, thereby tending to absorb vibration and reduce noise, rendering the motor relatively quiet in operation.

A spiral spring I1 has one end secured to the shaft 4 and the other end secured to the stud I6.

The armature A disc I8 is positioned between the sleeve I and the collar 8` and has a hole through which the head of the stud IB may extend. The disc I8 rotates with the armature and provides a cover or retaining wall for the spring II.

It is to be understood, of course, that the armature just described is to be used in connection with a stator primary such as is ordinarily used in a single phase induction moto-r.

When the line voltage is impressed upon the windings of the primary, not shown, a starting torque is produced between the field structure Y and the armature, causing the armature to rotate in a counter-clockwise direction, as indicated by the arrow, Fig. 2. It will be understood that when the motor is at rest and the power is olf, the arm 9 and the armature are in the position indicated in the drawing. When a starting torque is produced, the armature rotates with respect to the shaft and, therefore, with respect to the arm 9. The stud I6 rotates and strikes the exposed end of the pin I3, thereby eifecting the driving connection between the armature and the shaft 4. In the absence of torque between the field Structure and the armature, the tension of the spring Il causes the armature to rotate in a clockwise direction, moving the stud I6 away from abutment with the pin I3 and to a position on the opposite side of the arm 9, that is to say the position shown in the drawing.

kIt will thus be seen that, in the construction shown, rotation of the armature for a fixed distance independent of the load is permitted, thus allowing the armature to gain a momentum before connection with the load. The result is that the load is started with a torque between the primary and secondary which is greater than the stalled rotor starting torque, and in addition the inertia of the rotating armature enhances the starting effect.

It will be obvious that parts of the invention may be used without the whole, and that various changes may be made in the details of construction, within the scope of the appended claims, without departing from the spirit of this invention.

I claim:

1. An electric motor having a field structure, an armature free to rotate on its shaft, a projection on the armature, an arm secured to the shaft, a pin resiliently supported on the arm and having one end extending beyond one side thereof, resilient means connected between the shaft and the armature causing the projection to rest against one side of the arm in the absence of torque and permitting the projection to engage the extended end of the pin after the armature had effected a partial revolution under the influence of the field.

2. An electric motor having an armature free to rotate relative to a driving shaft, an engaging member projecting from the armature, an arm on the shaft adapted to be engaged on one side by one face of said member, resilient means adapted in the absence of motor torque to cause a relative movement between the shaft and the amature the major portion of one revolution bringing the other side of said arm into engagement with the other face of said member, and a resilient bumper on the driven face of the arm.

3. The combination of an external load adapted continuously to impose substantial mechanical resistance to a driving force, an alternatingcurrent motor of relatively-small direct starting capacity with relation to said load, said motor including a rotor, and spring-cushioned impact coupling means interposed between the rotor and the load and allowing sufcient free motion for starting.

4. In an alternating current induction motor having a relatively small starting torque, the combination including an armature free to rotate relative to a driving shaft, an engaging member projecting from the armature, an arm on the shaft adapted to be engaged on one side by one face of said member, and resilient means adapted in the absence of motor torque to cause a relative movement between the shaft and the armature the major portion of one revolution bringing `the other side of said arm into engagement with the other face of said member, whereby the armature is permitted to start and to ro tate initially the major portion of a revolution free from a load carried by the shaft and to then contact and drive the shaft.

5. In an alternating current induction motor having a relatively small starting torque, the combination including an armature free to rotate on a shaft, an` engaging member projecting from the armature, an arm on the shaft adapted. to be engaged on one side by one face of ysaid member, and resilient means adapted in the absence of motor torque to cause a relative movement between the shaft and the armature the major portion of one revolution bringing the other side of said arm into engagement with the other face of said member, whereby the armature is permitted to start and to rotate initially the major portion of a revolution free from a load carried by the shaft and to then contact and drive the shaft.

6. In an alternating current induction motor having a relatively small starting torque, the combination including an armature free to rotate relative to a driving shalt, an engaging member projecting axially from the armature, an arm extending radially from the shaft adapted to be engaged on one side by one face of said member, and resilient means adapted in the absence of motor torque to cause a relative movement betweenl the shaft and the armature the major portion of one revolution bringing the other side of said arm into engagement with the other face of said member, whereby the armature is permitted to start and to rotate initially the major portion of a revolution free from a load carried by the shaft and to then contact and drive the shaft.

7. The combination of a shaft to be driven, an alternating current motor of relatively small direct starting capacity with relation to the load to be carried by said shaft, said motor including a rotor and a driving connection between the shaft and the rotor including an abutment carried by one of said members and a spring-cushioned impact device carried by the other member and positionedto cooperate with said abutment and to permit a maximum of not less than one--half a revolution betweemsaid members before establishing a driving engagement between said abutment and said impact device.

8. The combination of a shaft to be driven, an alternating current motor of relatively small direct starting capacity with relation to the load to be carried by said shaft, said motor including a rotor and a driving connection between the shaft and the rotor including cooperating abutments carried by the shaft and rotor respectively and positioned to permit a relative rotation between the shaft and rotor of the major portion of one revolution, and resilient means interposed between the shaft and rotor and adapted to separate the abutments a maximum of not less than one-half a revolution upon the cessation of motor torque.

ALBERT C. DICKSON. 

